Method of applying a satisfactorily adhering,poorly reflecting,conductive layer to an insulating surface and electric discharge tube having a layer applied by said method

ABSTRACT

A SMOOTH CONDUCTIVE LAYER OF POOT REFLECTIVITY ON AN INSULATING SURFACE IN OBTAINED BY FIRST APPLYING A CHROMINUM NICKEL LAYER WHICH IS OXIDIZED BY HEATING IN IS APPLIED A NICKEL LAYER WHICH IS OXIDIZED BY HEATING IN AIR AT 250* CTO500*C.

United States Patent Office 3,813,293- Patented May 28, 1974 Int. Cl.C23b 5/50, 5/64 US. Cl. 117-217 2 Claims ABSTRACT OF THE DISCLOSURE Asmooth, conductive layer of poor reflectivity on an insulating surfaceis obtained by first applying a chromium-nickel layer from the vaporphase, to which layer is applied a nickel layer which is oxidized byheating in air at 250 C. to 500 C.

This application is a continuation of application Ser. No. 856,160 filedSept. 8, 1969, now abandoned.

The invention relates to a method of applying a satisfactorily adhering,poorly reflecting, conductive layer to an insulating surface,particularly to the inner wall of an electric discharge tube.

The invention furthermore relates to an electric discharge tube,particularly an image intensifier or a cathoderay tube provided with aconducting, poorly reflecting layer applied by said method to part ofthe inner surface of the tube bulb.

From French Patent Specification 806,867 it is known that the reflectionof a brilliant metal layer can be reduced by covering it with a blacklayer, for example, of nickel oxide. The nickel oxide is applied assuch, for example, by a suspension.

It is found that such a nickel oxide layer adheres poorly. This isparticularly disadvantageous when such a layer is applied in an electricdischarge tube, which is heated at a comparatively high temperatureduring degassing. The nickel oxide layer may then scale olf or particlesmay be released therefrom.

It has been found that a satisfactorily adhering, smooth conductivelayer with poor reflection can be applied to an insulating surface whenin accordance with the invention the surface is first coated by vapordeposition in vacuo with a chromium-nickel layer, to which a nickellayer is applied from the vapor phase, which is converted at leastpartly into nickel-oxide by heating in an oxidizing atmosphere. Itappears that the layer is conductive, adheres very satisfactorily to theinsulating surface and has a reflection of less than 10% of that of abrilliant aluminium layer for light of a wavelength of 5000 to 7000 A.

Such layers are quite suitable for partially covering the inner surfaceof the glass bulb of an electric discharge tube, particularly of animage intensifier or of a cathoderay tube. The oxidation of the nickellayer may be performed by heating in air at 250 C. to 500 C. Thethickness of the nickel layer may be about In.

What is claimed is:

1. A method of applying a satisfactorily adhering, smooth, conductinglayer of poor reflection to an insulating surface comprising the stepsof vapor depositing in vacuum a chromium-nickel layer on said surface,thereafter depositing a nickel layer about I thick on saidchromium-nickel layer, and heating the nickel layer in an oxidizingatmosphere to partially convert said nickel layer into nickel oxideuntil the reflection for light of a wave-length between 5000 and 7000 A.is less than 10%.

2. A method as claimed in claim 1 wherein the nickel layer is heated inair at 250 C. to 500 C.

References Cited UNITED STATES PATENTS 2,935,717 5/1960 Solow 117217 X2,927,048 3/ 1960 Pritikin 117-217 X 3,472,691 10/1969 Kooy et a1 1172173,462,723 8/ 1969 Philips 117217 X 3,112,222 11/1963 Alger 117-217 LEOND. ROSDOL, Primary Examiner M. F. EPOSITO, Assistant Examiner US. Cl.X.R.

